Fertilizer tank bursts at Mockonema plant

A 200,000-gallon tank of ammonium phosphate fertilizer burst at McGregor Company’s Mockonema manufacturing plant Monday afternoon. The rupture gushed approximately 100,000 gallons of the liquid fertilizer onto the ground and across the Endicott Road.

The rupture occurred at 2:30 p.m., when employees were mixing ammonia and uric acid to make the ammonium phosphate.

No one was injured when the tank began gushing fluid. Jim Lemon said Chris Hille was watching over the mixing process when the tank burst.

“He said he heard a crunch of metal, looked up and just saw this stream of green flowing out, over and under rail cars and onto the road,” said Jim Lemon, McGregor safety-regulatory- environmental coordinator. “It was like a little mini-tsunami right here at Mockonema.”

A crew of about 30 McGregor employees worked into the night Monday and all day Tuesday to clean up the scene. They were back on clean-up duty at press time.

About 40,000 gallons of the spilled liquid that pooled in a drainage ditch between the plant and the highway have been pumped into another tank.

Lemon Tuesday estimated another 10,000 gallons remained to be pumped.

The rest was absorbed into the ground nearby. Contaminated rock and soil will be dug up and spread across some of the company’s nearby farm ground.

Ammonium phosphate is mildly caustic, but is not a hazardous material, which meant emergency responders were not called in.

The steel tank was built in the late-1970s. Lemon said the state Department of Agriculture requires monthly inspections of the tanks. None of those checks had shown any weakness in the tank.

Officials with the state departments of agriculture and ecology inspected the scene.

Tanks at the plant are in a containment facility, but Lemon said the facility is intended to control small leaks, not catastrophic tank failures.

The rupture happened just when the company was ramping up fertilizer production for the fall seeding season.

Seven tanker cars of uric acid are on the railroad right beside the plant. None were seriously damaged when the tank ruptured.

McGregor’s Mockonema mixing plant supplies fertilizer to the company’s 43 retail facilities.

In addition to the tank, the spill wiped out a small pump house and dimpled a water tank next to the phosphate tank. The water tank will have to be removed.

Lemon said the buildings were insured.

Salvage work was being done by Palouse River Rock and by the Miller family of Cheney.

Fertilizer recovered from the ground will be filtered and processed for future sale.